LIGHTWEIGHT SUPPORT STRUCTURE, METHOD OF PRODUCING A LIGHTWEIGHT SUPPORT STRUCTURE, COMPOSITE SANDWICH PANEL AND METHOD OF PRODUCING A COMPOSITE SANDWICH PANEL
A lightweight support structure includes a composite sandwich panel having a first face sheet and a lightweight core attached to the face sheet and an essentially rotationally symmetric cut-out extending through the first face sheet and into the lightweight core. The cut-out has an essentially rotationally symmetric inner cut-out and outer cut-out arranged essentially concentric with respect to each other, providing for a support there between. The support has a core support cut from the lightweight core and a support face sheet disc on top, cut from of the first face sheet. A rotationally symmetric insert is fitted into the cut-out for load application and/or anchorage of various components into and onto the sandwich panel.
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The present invention relates to a lightweight support structure comprising a composite sandwich panel and a load application and/or anchorage element, a method of producing such a lightweight support structure. The present invention further relates to a composite sandwich panel and a method of producing such a composite sandwich panel.
BACKGROUND OF THE INVENTIONComposite sandwich panels are a special type of composite materials/structures fabricated by attaching two relatively thin but stiff face sheets to a lightweight but thick core. The core material is normally of relatively low strength material, but its higher thickness provides the sandwich composite with high bending stiffness with overall low density. Composite sandwich panels are commonly made by layering a core material between two thin layers that provide strength in tension. The lightweight core is usually attached to the face sheets by adhesive bonding and/or metal brazing. This forms a plate-like assembly.
The face sheets are usually laminates of glass and/or carbon fiber-reinforced thermoplastics and/or thermoset polymers such as unsaturated polyesters, epoxies. Alternatively sheet metal, preferably of lightweight metals such as aluminium, may also be employed for face sheets of sandwich panels. The lightweight core of sandwich panels are usually open- and/or closed-cell-structured foams (such as polyvinylchloride, polyurethane, polyethylene or polystyrene foams, syntactic foams) or open- and/or closed-cell metal foams, preferably of lightweight metals such as aluminium.
Quite often honeycomb structures, preferably of lightweight metals such as aluminium or fibreglass and advanced composite materials, are preferred as lightweight core due to their excellent strength to weight ratio. Honeycomb structures are structures that have the geometry of a honeycomb to allow the minimization of the amount of used material to reach minimal weight. The geometry of honeycomb structures can vary widely but the common feature of all such structures is an array of hollow cells formed between thin vertical walls. The cells are often columnar and hexagonal in shape. A honeycomb shaped structure provides a material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties.
The behaviour of a composite sandwich panels is orthotropic, hence the panels react differently depending on the orientation of the structure. Therefore it is necessary to distinguish between in-plane forces and out-of-plane forces. In a composite sandwich panel the face sheets are provided for transferring in-plane forces while the lightweight core is provided for high out-of-plane compression resistance.
Composite sandwich panels are widely used where flat or slightly curved surfaces are needed and their high strength-to-weight ratio is valuable. They are widely used in the aerospace industry for this reason, and have been featured in aircraft and rockets for long time. While sandwich panels are capable of carrying high loads, load application and/or anchorage of various components requires specific solutions due to said different strength depending on the direction of the applied forces. In order to make full use of the advanced properties of a composite sandwich panel and to avoid damage thereof, the static and dynamic loads from attached components such as lenses, antennas, etc. must be optimally transferred into the structure. As aircrafts, spacecrafts, rockets, satellites, etc. are subject to strong vibrations on the order of up to 100 g, the loads on the attachment points of components to the sandwich panels carrying them are very high.
To satisfy these strict requirements, the anchorage of components and load application may be achieved by means of inserts fitted into the sandwich structure, such as the insert disclosed in GB 1328429. At the same time, the inserts should be fitted to sit flatly within the composite sandwich panel. This process is currently performed mainly by hand or by complex processes involving labour-intensive production steps requiring various tools and auxiliary means. For example the insert of GB 1328429 is mounted by using an auxiliary plate parallel to the face sheet of the composite sandwich panel, the auxiliary plate being attached to the insert during its insertion into the panel and during the curing of the adhesive which adheres the insert into the panel. However, this can take up to 48 hours which makes this process very inefficient. Furthermore quite often accidental leakage of the adhesive might bond the auxiliary plate to the insert, which might lead to the insert being stressed or in the worst case even pulled out of the sandwich panel during removal of the auxiliary plate, thereby damaging the entire sandwich panel. In addition, known inserts for load application into composite sandwich panels must be very precisely aligned with the cut-outs into which they are mounted, making automated assembly impossible or very costly.
TECHNICAL PROBLEM TO BE SOLVEDThe objective of the present invention is thus to provide a lightweight support structure and corresponding method of producing a lightweight support structure comprising a composite sandwich panel which allows safe and strong anchorage of various components and optimal load application into such composite sandwich panels while drastically reducing the efforts of providing such without the need of various tools and aids.
A further objective of the present invention is to provide a composite sandwich panel and corresponding method of producing a composite sandwich panel suitable for receiving an insert allowing the provision of safe and strong anchorage of various components and optimal load application into such composite sandwich panels.
SUMMARY OF THE INVENTIONThe above identified objective of providing a lightweight support structure which allows safe and strong anchorage of various components and optimal load application into such composite sandwich panels while drastically reducing the efforts of providing such without the need of various tools and aids is achieved by a lightweight support structure comprising a composite sandwich panel. The composite sandwich panel comprising a first face sheet for transferring in-plane forces; a lightweight core configured for high transverse shear strength, said lightweight core being attached to the face sheet, the composite sandwich panel further comprising an essentially rotationally symmetric cut-out extending through the first face sheet and into said lightweight core. The cut-out in the composite sandwich panel comprises an essentially rotationally symmetric inner cut-out and an essentially rotationally symmetric outer cut-out arranged essentially concentric with respect to each other, providing for a support inbetween, said support comprising a core support cut from said lightweight core and a support face sheet disc on top, cut from of said first face sheet. In addition, the lightweight support structure further comprises an essentially rotationally symmetric insert fitted into said cut-out for load application and/or anchorage of various components into, respectively onto the composite sandwich panel, the core support being preferably compressed so as to allow said insert to lie flatly inside the composite sandwich panel.
The objective of the present invention of providing a method of producing a lightweight support structure comprising such a composite sandwich panel which allows safe and strong anchorage of various components and optimal load application into such composite sandwich panels while drastically reducing the efforts of providing such without the need of various tools and aids is solved by a method of producing a lightweight support structure comprising the steps:
providing a composite sandwich panel having: a first face sheet for transferring in-plane forces; a lightweight core attached to the first face sheet,
cutting an essentially rotationally symmetric inner cut-out and an essentially rotationally symmetric outer cut-out into said composite sandwich panel by cutting through the first face sheet and into said lightweight core, wherein the inner cut-out and the outer cut-out are arranged essentially concentric with respect each other,
by cutting said inner cut-out and outer cut-out, providing a support inbetween, said support comprising a core support cut from said lightweight core and a support face sheet disc on top, cut from of said first face sheet;
fitting a rotationally symmetric insert into said cut-out for load application and/or anchorage of various components into respectively onto the composite sandwich panel.
The cut-out is configured for receiving a rotationally symmetric insert for load application and/or anchorage of various components into respectively onto the composite sandwich panel while said support is configured for stabilizing said insert within the composite sandwich panel.
The above identified objective of providing a composite sandwich panel suitable for receiving an insert allowing the provision of a safe and strong anchorage of various components and optimal load application into such composite sandwich panels is achieved by a composite sandwich panel comprising: a first face sheet for transferring in-plane forces and a lightweight core attached to the first face sheet. The composite sandwich panel is provided with rotationally symmetric cut-out extending through the first face sheet and into said lightweight core. The insert cut-out comprises an essentially rotationally symmetric inner cut-out and an essentially rotationally symmetric outer cut-out arranged essentially concentric with respect to each other, providing for a support inbetween, comprising a core support cut from said lightweight core and a support face sheet disc, cut from of said first face sheet. The cut-out is configured for receiving a rotationally symmetric insert for load application and/or anchorage of various components into respectively onto the composite sandwich panel, preferably by form-fitting and/or force-fitting while the support is configured for stabilizing said insert within the composite sandwich panel.
The above identified objective of providing a method of producing a composite sandwich panel suitable for receiving an insert allowing the provision of a safe and strong anchorage of various components and optimal load application into such composite sandwich panels is achieved by a method of producing a composite sandwich panel comprising the steps of:
providing a composite sandwich panel having a first face sheet for transferring in-plane forces and a lightweight core attached to the first face sheet;
cutting an essentially rotationally symmetric inner cut-out and an essentially rotationally symmetric outer cut-out into said composite sandwich panel by cutting through the first face sheet and into said lightweight core, wherein the inner cut-out and the outer cut-out are arranged essentially concentric with respect each other;
by cutting said inner cut-out and outer cut-out, providing a support inbetween, said support comprising a core support cut from said lightweight core and a support face sheet disc on top, cut from of said first face sheet;
configuring said cut-out for receiving a rotationally symmetric insert for load application and/or anchorage of various components into respectively onto the composite sandwich panel, preferably by form-fitting and/or force-fitting; and
configuring said support for stabilizing said insert within the composite sandwich panel.
ADVANTAGEOUS EFFECTSThe most important advantage of the present invention is that the lightweight support structure respectively the composite sandwich panel can be provided with a strong and precise anchorage of various components and optimal load application into such composite sandwich panels while drastically reducing the efforts of providing such without the need of various tools and aids.
Further characteristics and advantages of the invention will in the following be described in detail by means of the description and by making reference to the drawings. Which show:
Note: The figures are not drawn to scale, are provided as illustration only and serve only for better understanding but not for defining the scope of the invention. No limitations of any features of the invention should be implied form these figures.
Certain terms will be used in this patent application, the formulation of which should not be interpreted to be limited by the specific term chosen, but as to relate to the general concept behind the specific term.
The face sheets 10, 20 of the composite sandwich panel 5 comprise(s) one or more of the following:
laminates of glass and/or carbon fiber-reinforced thermoplastics and/or thermoset polymers such as unsaturated polyesters, epoxies; and/or
sheet metal, preferably of lightweight metals such as aluminium.
While most figures (except for
open- and/or closed-cell-structured foams such as polyvinylchloride, polyurethane, polyethylene or polystyrene foams, syntactic foams;
open- and/or closed-cell metal foam, preferably of lightweight metals such as aluminium;
honeycomb structures, preferably of lightweight metals such as aluminium or fibreglass and advanced composite materials.
The lightweight core 15 is preferably attached to the first face sheet 10 and/or said second face sheet 20 by adhesive bonding and/or metal brazing. An alternative lightweight core 15 in the form of a foam is illustrated on
As seen on
As illustrated on the figures, according to the most advantageous embodiment of the present invention, the outer cut-out 32 is cut as an essentially hollow cylinder (tubular) while the inner cut-out is 31 is cut as an essentially solid cylinder. Nonetheless, due to the potential non-homogeneity of the lightweight core 15, the outer cut-out 32 and the inner cut-out 31 (resulting form said hallow respectively solid cylindrical cuts) do not necessarily have cylindrical outer surfaces. For this reason, the outer cut-out 32 respectively the inner cut-out 31 are referred to in the present application as essentially rotationally symmetric cut-outs. This is well illustrated on
The insert 50 is configured such as to fit into the cut-out 30 in the composite sandwich panel 5. Accordingly, the insert 50 comprises an essentially rotationally symmetrical inner insert ring 51 and outer insert ring 52 corresponding to the inner cut-out 31 respectively outer cut-out 32 of the composite sandwich panel 5. The illustrated insert 50 and its inner respectively outer insert rings 51, 52 are of a cylindrical shape. However, conical shapes can be also beneficial. Furthermore, the outer insert ring 52 is arranged with respect to said inner insert ring 51 such that as to provide an insert trench 54 inbetween for receiving the support 40 of the composite sandwich panel 5.
The inner insert ring 51 and an outer insert ring 52 are connected by an insert connecting portion 53 inbetween. The insert connecting portion 53 is preferably flat so that the insert 50 may be fitted flat within the composite sandwich panel 5. Furthermore the thickness of the insert connecting portion 53 is chosen to correspond to a compression depth of the lightweight core 15 of the composite sandwich panel 5 (described below with reference to
In its most preferred embodiment, the insert 50 comprises a receiving area 55 for receiving a fixture 100 for attaching and/or anchoring of various components into respectively onto the composite sandwich panel 5. The figures show a receiving area 55 as a cylindrical opening in the insert 50 partially within the inner insert ring 51. Fixtures may be attached to the receiving area 55 by form-fitting, press-fitting, by means of adhesive, by means of a thread therein, etc. In a particularly preferred embodiment, the receiving area 55 of the insert 50 is provided with a distorted thread to prevent the fixture 100 thread-locked therein from loosening due to vibrations.
A particularly preferred embodiment of the insert 50 is a self-cutting insert 50 wherein the inner insert ring 51 and outer insert ring 52 are at least partially provided with an abrasive coating (such as diamond particle coating) and/or a saw-tooth geometry. By rotating the insert 50 around its symmetry axis, the insert 50 is able to cut the inner cut-out 31 and an outer cut-out 32 into the composite sandwich panel 5 by cutting through the first face sheet 10 and into said lightweight core 15. After self-cutting the cut-out 30, the self-cutting insert 50 is fit into the cut-out 30, preferably by form-fitting and/or force-fitting and/or by means of an adhesive.
Figures
The self-alignment of the insert 50 allows an automated mounting of the insert 50 into the composite sandwich panel 5. Furthermore, the self-alignment allows for a very tight fit of the insert 50 within the cut-out 30, which in turn prevents leakage of adhesive. At the same time, the tight fit of the insert 50 within the cut-out 30 ensures that the insert 50 must not be stabilised within the composite sandwich panel 5, even if the adhesive (or other alternative means of securing the insert) has not yet re4acheds it final bonding.
As is illustrated on
As seen on
As illustrated on
It will be understood that many variations could be adopted based on the specific structure and method hereinbefore described without departing from the scope of the invention as defined in the following claims.
Claims
1. A lightweight support structure (1) comprising: characterized in that:
- a composite sandwich panel (5) comprising:
- a first face sheet (10);
- a lightweight core (15) attached to the first face sheet (10);
- an optional second face sheet (20) attached to the lightweight core (15) opposite the first face sheet (10); and
- an essentially rotationally symmetric cut-out (30) extending through the first face sheet (10) and into said lightweight core (15);
- a rotationally symmetric insert (50) fitted into said cut-out (30) for load application and/or anchorage of various components into, respectively onto the composite sandwich panel (5),
- the cut-out (30) comprises an essentially rotationally symmetric inner cut-out (31) and an essentially rotationally symmetric outer cut-out (32) arranged essentially concentric with respect to each other, providing for a support (40) inbetween;
- said support (40) comprises a core support (41) cut from said lightweight core (15) and a support face sheet disc (42) on top, cut from of said first face sheet (10); and
- the core support (41) is preferably compressed so as to allow said insert (50) to lie flatly inside the composite sandwich panel (5).
2. A lightweight support structure (1) according to claim 1, characterised in that said insert (50) comprises: wherein said outer insert ring (52) is arranged with respect to said inner insert ring (51) such as to provide an insert trench (54) inbetween for receiving the support (40) of the composite sandwich panel (5); and
- an inner insert ring (51) configured to be receivable within the inner cut-out (31) of the composite sandwich panel (5);
- an outer insert ring (52) configured to be receivable within the outer cut-out (32) of the composite sandwich panel (5),
- an insert connecting portion (53) connecting said inner insert ring (51) with said outer insert ring (52), configured to be restable on the support face sheet disc (42) of the support (40)
- preferably an insert receiving area (55) for receiving a fixture (100) for attaching and/or anchoring of various components into respectively onto the composite sandwich panel (5).
3. A lightweight support structure (1) according to claim 1, characterised in that the insert (50) is a self-cutting insert, its inner insert ring (51) and outer insert ring (52) being at least partially provided with an abrasive coating and/or a saw-tooth geometry configured such that—by rotation of the insert (50) around its symmetry axis—the inner insert ring (51) respectively outer insert ring (52) are able to cut said inner cut-out (31) respectively outer cut-out (32) into the composite sandwich panel (5).
4. A lightweight support structure (1) according to claim 1, characterised in that the insert (50) is fitted into the cut-out (30) of the composite sandwich panel (5) by form-fitting and/or force-fitting and/or soldering and/or brazing and/or welding and/or by means of an adhesive.
5. A lightweight support structure (1) according to claim 2, characterised in that an adhesive (56) is provided in said insert trench (54) and the insert (50) comprises at least one channel (57) extending from said trench (54) through the outer insert ring (52), configured such that upon fitting of the insert (50) into the cut-out (30) of the composite sandwich panel (5), the support face sheet disc (42) forces said adhesive (56) through said at least one channel (57).
6. Method of producing a lightweight support structure (1) comprising the steps: characterized by the steps of: wherein said cut-out (30) is configured for receiving a rotationally symmetric insert (50) for load application and/or anchorage of various components into respectively onto the composite sandwich panel (5); and wherein said support (40) is configured for stabilizing said insert (50) within the composite sandwich panel (5).
- providing a composite sandwich panel (5) comprising: a first face sheet (10), and a lightweight core (15) attached to the first face sheet (10),
- cutting an essentially rotationally symmetric inner cut-out (31) and an essentially rotationally symmetric outer cut-out (32) into said composite sandwich panel (5) by cutting through the first face sheet (10) and into said lightweight core (15), wherein the inner cut-out (31) and the outer cut-out (32) are arranged essentially concentric with respect each other,
- by cutting said inner cut-out (31) and outer cut-out (32), providing a support (40) inbetween, said support (40) comprising a core support (41) cut from said lightweight core (15) and a support face sheet disc (42) on top, cut from of said first face sheet (10);
- fitting a rotationally symmetric insert (50) into said cut-out (30) for load application and/or anchorage of various components into respectively onto the composite sandwich panel (5),
7. Method of producing a lightweight support structure (1) according to claim 6, characterised in that the step of fitting said insert (50) into said cut-out (30) comprises:
- fitting an inner insert ring (51) of the insert (50) into the inner cut-out (31) of the composite sandwich panel (5);
- fitting an outer insert ring (52) of the insert (50) into the outer cut-out (32) of the composite sandwich panel (5);
- resting an insert connecting portion (53) connecting said inner insert ring (51) with said outer insert ring (52) on the support face sheet disc (42) of the support (40) wherein upon being fitted, the insert (50) is self-aligned with the cut-out (30) preferably by means of a tapered conical section (51.5) of the inner insert ring (51) and/or a tapered conical section (52.5) of the outer insert ring (52).
8. Method of producing a lightweight support structure (1) according to claim 7, characterised in that the step of fitting said insert (50) into said cut-out (30) further comprises the following steps: a) compressing said core support (41) by means of said insert connecting portion (53) exercising pressure on the support face sheet disc (42), the core support (41) being preferably compressed by a compression (Δ) equal to a thickness (D) of said insert connecting portion (53); b) measuring an unevenness (U) between a top surface of the insert (50) and a top surface of the first face sheet (10); c) increasing said a compression (Δ); d) repeating steps a) to c) until said unevenness (U) is below a predetermined unevenness tolerance, i.e. the insert (50) lies flatly inside said composite sandwich panel (5).
9. Method of producing a lightweight support structure (1) according to claim 6, characterised in that said rotationally symmetric insert (50) is fitted into the cut-out (30) of the composite sandwich panel (5) by form-fitting and/or force-fitting and/or soldering and/or brazing and/or welding and/or by means of an adhesive.
10. Method of producing a lightweight support structure (1) according to claim 5, characterised in that said inner cut-out (31) and outer cut-out (32) are self-cut into the composite sandwich panel (5) by rotation of the insert (50) around its symmetry axis, wherein the inner insert ring (51) and outer insert ring (52) of the insert (50) are at least partially provided with an abrasive coating and/or a saw-tooth geometry.
11. Method of producing a lightweight support structure (1) according to claim 6, characterised in that said inner cut-out (31) and outer cut-out (32) are cut into the composite sandwich panel (5) by means of a cutter tool (70) comprising an inner cutting ring (71) and an outer cutter ring (72) corresponding to said inner cut-out (31) respectively said outer cut-out (32).
12. A composite sandwich panel (5) comprising: wherein:
- a first face sheet (10);
- a lightweight core (15) attached to said first face sheet (10); and
- an optional second face sheet (20) attached to the lightweight core (15) opposite the first face sheet (10);
- the composite sandwich panel (5) is provided with rotationally symmetric cut-out (30) extending through the first face sheet (10) and into said lightweight core (15);
- the insert cut-out (30) comprises an essentially rotationally symmetric inner cut-out (31) and an essentially rotationally symmetric outer cut-out (32) arranged essentially concentric with respect to each other, providing for a support (40) inbetween, comprising a core support (41) cut from said lightweight core (15) and a support face sheet disc (42), cut from of said first face sheet (10);
- said cut-out (30) is configured for receiving a rotationally symmetric insert (50) for load application and/or anchorage of various components into respectively onto the composite sandwich panel (5), preferably by form-fitting and/or force-fitting; and
- said support (40) is configured for stabilizing said insert (50) within the composite sandwich panel (5).
13. Method of producing a composite sandwich panel (5) comprising the steps:
- providing a composite sandwich panel (5) comprising:
- a first face sheet (10);
- a lightweight core (15) attached to the first face sheet (10);
- an optional second face sheet (20) attached to the lightweight core (15) opposite the first face sheet (10);
- cutting an essentially rotationally symmetric inner cut-out (31) and an essentially rotationally symmetric outer cut-out (32) into said composite sandwich panel (5) by cutting through the first face sheet (10) and into said lightweight core (15), wherein the inner cut-out (31) and the outer cut-out (32) are arranged essentially concentric with respect each other,
- by cutting said inner cut-out (31) and outer cut-out (32), providing a support (40) inbetween, said support (40) comprising a core support (41) cut from said lightweight core (15) and a support face sheet disc (42) on top, cut from of said first face sheet (10);
- configuring said cut-out (30) for receiving a rotationally symmetric insert (50) for load application and/or anchorage of various components into respectively onto the composite sandwich panel (5), preferably by form-fitting and/or force-fitting; and
- configuring said support (40) for stabilizing said insert (50) within the composite sandwich panel (5).
14. Method of producing a composite sandwich panel (5) according to claim 13, characterized in that said inner cut-out (31) and outer cut-out (32) are self-cut into the composite sandwich panel (5) by an inner insert ring (51) respectively an outer insert ring (52) of an insert (50) for load application and/or anchorage of various components into respectively onto the composite sandwich panel (5), by rotation of said insert (50) around its symmetry axis, said inner insert ring (51) respectively an outer insert ring (52) being at least partially provided with an abrasive coating and/or a saw-tooth geometry.
15. Method of producing a composite sandwich panel (5) according to claim 13, characterized in that said inner cut-out (31) and outer cut-out (32) are cut into the composite sandwich panel (5) by means of a cutter tool (70) comprising an inner cutting ring (71) and an outer cutter ring (72) corresponding to said inner cut-out (31) respectively said outer cut-out (32).
Type: Application
Filed: Dec 10, 2013
Publication Date: May 5, 2016
Patent Grant number: 9874306
Applicant: RUAG SCHWEIZ AG, RUAG SPACE (Zürich)
Inventors: Gregor BURKHARD (Olten), Dominik Christian NÄGELI (Amriswil)
Application Number: 14/777,913